Hepatitis C virus (HCV) is the most common chronic blood-borne infection in the US: an estimated 2.7 million Americans have been infected with the virus. Although the prevalence of HCV infection in the population is well established, the public health impact of liver disease caused by HCV remains uncertain. Based on established resources for population-based research in Olmsted County (the Rochester Epidemiology Project), we have already established a registry of all community residents presently dia.qnosed with HCV. In this study, we propose to screen community residents for HCV and then determine the impact of HCV infection in the community. In Aim 1, we will measure the prevalence of HCV which has not previously been dia.qnosed by screening the serum of Olmsted County residents of ages 30 to 49 years for HCV. For screening, we will utilize an established method to obtain serum samples from the majority of the target population in the community. In Aim 2, we will compare the prevalence and severity of liver disease, health status, quality of life and comorbidity profile among three groups of community residents, namely those with established HCV diagnosis, those with HCV infection discovered only by screening, and those without HCV infection. In Aim 3, based on these three groups, we will measure community-wide healthcare resource utilization related to HCV, independent of effects of comorbid conditions, particularly substance abuse and mental health problems. The results of this work will address the substantial .qap between patient outcome data derived from referral patient samples and prevalence data based on population surveys, by providing key information about the impact of HCV on morbidity and health of the maiority of Americans whose HCV infection remains undetected. My long-term goal is to establish a comprehensive patient-oriented research program in viral hepatitis and liver disease, encompassing epidemiology, survival statistics, quality of life, and health services research. Resources created by the current project, namely detailed clinical information and biologic specimens from a large cohort of community residents with HCV, will provide future opportunities to study natural history, virologic and host prognostic determinants of progression, and effectiveness of community-based interventions on HCV outcomes.